Movie producer William Castle was known in the 1950s for his low-quality horror films. In 1961, Castle did something totally unique in movie history: he let the audience choose the ending to his movie. Castle's movie, Mr. Sardonicus, was about a crazed, reclusive killer. Near the end of the film, ushers stopped the film and allowed audiences to vote on whether the killer should live or die. Then, the ushers ran the ending that the audience chose. The audience always chose death for the bad guy. It's a good thing human nature is so predictable. William Castle was counting on it. You see, he only filmed one ending to his movie, not two. He was so sure that the aud…